1. Field of the Invention
This invention relates to a process for the manufacture of polyurethane non-cellular, molded elastomers or cellular elastomers wherein a hydroxyl group-containing prepolymer is divided into two components, A and B, in a weight ratio of about 80:20 to 20:80. An NCO group containing NDI polyurethane adduct is prepared by reacting component A with 1,5-naphthylene diisocyanate (NDI). This adduct is subsequently reacted with a mixture of component B with materials selected from the group consisting of chain extenders, cross-linking agents, water and mixtures thereof. Conventional auxiliaries and additives may also be incorporated with component B.
2. Prior Art
Polyurethane elastomers which can be processed by thermoplastic means, based primarily on linear polyester polyols of aliphatic dicarboxylic acids and alkylene glycols, hydroxy carboxylic acids or polyether polylols based on polytetrahydrofuran are part of the current state of the art. In survey form, these polyurethane elastomers are described, for instance, in "Urethanes in Elastomers and Coatings", Technomic Publishing Company, 256 West State Street, Westport, Connecticut, U.S.A., 1973, pages 201 to 230, or in the Plastics Handbook, Vol. VII, Polyurethanes by R. Vieweg and H. Hoechtlen, Carl Hanser Publishers, Munich, 1966, starting on page 206.
An overview of known heat-curable, non-thermoplastic polyurethane molding resins is given in Polyurethanes Chemistry and Technology by J. H. Saunders and K. C. Frisch, Part II, beginning on page 758 (Interscience Publishers, 1964).
In many applications, it is desirable to use 1,5-naphthylene diisocyanate (NDI) in addition to other organic diisocyanates for the manufacture of polyurethane elastomers. This is particularly desirable for products having good thermal resistance. A drawback in processing NDI is that it has a solidification point of 127.degree. C. and cannot be reacted by the one-shot process as employed, for example, with hexamethylene diisocyanate, toluene diisocyanate, or 4,4'-diphenylmethane diisocyanate. Non-cellular molding elastomers and cellular elastomers based on NDI can therefore be produced only according to the prepolymer process.
In the manufacture of non-cellular as well as cellular polyurethane elastomers from NDI according to the prepolymer process, the NCO group-containing prepolymer and the "cross-linking agent" and/or water as blowing agent must be reacted in extremely unfavorable quantity ratios. Thus, for instance, 100 parts of NCO group-containing prepolymers and approximately 0.5 to 3 parts of "cross-linking agents" must be mixed quickly and intensively for the manufacture of cellular elastomers. This not only requires special mixers, but also extremely accurately operating metering pumps. When exposed to continuous loads, such mixtures and metering pumps are predominantly susceptible to technical failure and demand high maintenance expenditure.
The purpose of this invention is to produce cellular polyurethane elastomers or non-cellular molding elastomers based on NDI using commonly-applicable processing and metering devices. The basically known raw materials are to be used in this case also.